This is a breakout board for the Arduino Pro Mini 3.3V/5V 8/16Mhz provides an ICSP connector, allowing you to use a programmer to rewrite the boot loader, or to download sketches without a bootloader. I use it with a USBTinyISP programmer. I've also replicated the FTDI header which can be useful if you don't want to solder pins to the serial programming pins on the Arduino Pro Mini (for asthetic reasons, or if you only plan to upload a sketch to it just once). You'll need to populate the 0.1uF capacitor if you wish to use this feature. * Untested -- will remove this comment once I've fabricated the board and confirmed it works ok*